Band 42, Heft 9

Kurzfassung Die Verwendung von Formgedachtnislegierungen fur Mikroaktuatoren stellt ein potentielles Anwendungsfeld dar, wobei hier neben den Nickel-Titan-Legierungen auch Legierungen auf Kupfer- Basis ihre Einsatzmoglichkeiten finden, da diese hohere Schalttemperaturen erreichen konnen und kostengunstiger sind. Im Rahmen dieser Arbeit wurden dunne Bander aus CuAlNi-Legierungen durch Melt-Spinning hergestellt. Mittels dieses Verfahrens konnen durch geeignete Wahl der Prozessparameter Bander mit einer Dicke im Bereich von 50–250 μm produziert werden. Die Untersuchung des Gefuges und der Struktur erfolgte mit herkommlichen Untersuchungsmethoden. Problematisch war hier vor allem die Probenpraparation aufgrund der geringen Groöe der Proben. Die Umwandlungstemperaturen wurden durch DSC-Messungen bestimmt. Ein nachfolgendes Walzen konnte die Oberflachenbeschaffenheit und Homogenitat der Bander im Hinblick auf die Dicke entscheidend verbessern.

A survey is made on the application of some metallographic methods for the analysis of martensitic reactions. In this context the following aspects are discussed: Reverse reactions can be martensitic, to restore faultlessly the austenite, not fully reversible (defects accumulate), or diffusion controlled. In the last case austenite b must form by new nucleation and growth (crystallographic irreversibility). Then no surface upheavals form.

Ti 4 Ni 2 O, Ti 4 Ni 2 N, TiC and Ti 2 Ni are brittle compounds usually formed during production and processing of the Ti-Ni SMA alloys. These compounds adversely affect on workability and shape memory properties of the alloy. This paper presents most recent findings related to the morphologies of various inclusions and Ti-Ni phases formed during and after vacuum induction melting and casting of Ti-45wt.% Ni material. Cast samples were mechanically and/or electrolytically polished and etched. Extensive optical and scanning electron microscopic studies were carried out to characterize the composition and microstructure of the as cast Ti-Ni alloys. Results indicated that mechanical polishing followed by etching was not proficient to reveal sufficient data on physical specifications and morphological changes of the born brittle oxide and nitride and carbide phases. An innovative set of electropolishing/etching conditions was, therefore, prescribed to yield detailed information on morphologies of the brittle phases. Experimental conditions were devised for characterization of the Ti 2 Ni precipitates, as well.

Goldsmith has been practiced since as early as 4000 BC but the microstructure examination of precious metals is still an enigma to many metallographers. The precious metal industry, historically secretive, was slow to share technology. In this study, the effects of the electrolytic etching reagents and etching parameters on microstructure for a gold alloy with composition of 91.60 Au – 7.44 Cu – 0.63 Ag – 0.21 Zn – 0.12 Ni (in wt. %) has been investigated. The determination of the optimum etching conditions has been performed using an etching reagent of 32 % HCl.